Overload circuit breaker for high currents



Aug. 4, 1964 J. ELLENBERGER OVERLOAD CIRCUIT BREAKER FOR HIGH CURRENTS Filed March 21, 1961 3 Sheets-Sheet 1 FIG-3 INVENTOR: J'E/Ien barge! ATT'QRNESS Aug- 1954 J. ELLENBERGER 3,143,617

OVERLOAD CIRCUIT BREAKER FOR HIGH CURRENTS Filed March 21. 1961 Q 3 Sheets-Sheet 2 4" 5 I 9 l/WENI'OR J. Ellenber er' ATT KNEES A g 1964 J. ELLENBERGER OVERLOAD CIRCUIT BREAKER FOR HIGH CURRENTS 3 Sheets-Sheet 3 Filed. March 21. 1961 FIG, 12

FIG. 1.!

f/VVENTOR: J. E/[enber b'er OLZQA ATTorLNESs 3,143,617 Ice Patented Aug. 4,1964

assignor to Ellenberger & Poensgen G.m.b.H., Altdorf,

near Nurnberg, Germany Filed Mar. 21, 1961, Ser. No. 97,309 Claims priority, application Germany Mar. 23, 1960 7 Claims. (Cl. 200-122) The present invention relates to an overload circuit breaker for high currents.

There has always been and still is a considerable need for smaller and more economic circuit breakers which have a high capacity. This is especially due to the progress in electrification whereby the occurrence of short-circuit currents in public power lines has increased considerably. It is therefore often necessary to switch oif a much higher than the normal power. If the circuit breakers which are installed for this purpose are insufiicient, it is necessary to replace them by new circuit breakers 'which should not require any larger space but should comply with the increased requirements and be capable of switching off the high short-circuit currents which might occur in the power lines.

Ithas so far been conventional to provide overload circuit breakers with thermal and electromagnetic releasing devices in which the thermal release occurred if there was a thermal overload, while the magnetic release took place if short-circuit currents occurred. It is, however, also known to provide overload circuit breakers merely with thermal releasing devices.

The present invention relates to a circuit breaker of the last-mentioned type which is operated by a push-button and provided with a thermal release and a trip-free release, and has a contact bridge in the form of an angular lever which is freely pivotable on projections on a control bridge which is rigidly connected by means of a control rod to the pushbutton which is acted upon by a return spring. This contact bridge is movable along the control rod in the axial direction thereof against the action of a spring which is supported on the control bridge. When the circuit breaker is switched off, the contact bridge is pressed by the pivot projections against an inclined stop surface, while when it is switched on, the contact bridge is taken along by the control bridge and moved to a position in which it engages with and is arrested by a detent on the bimetallic strip.

There has been a prior disclosure of an overload circuit breaker of the type as described above which, however,

.can only be used for switching otf medium-sized and smaller currents. In contrast to this, it is the object of the present invention to provide a circuit breaker of this type which is of the smallest possible size and designed for reliably switching off very high currents, for example,

5000 amperes at 125 volts of alternating current.

This object is attained according to the invention primarily by connecting the free end of the bimetallic strip to the contact bridge by means of a flexible conductor and by providing the walls of the housing of the circuit breaker at the area adjacent to the fixed contact with ribs which extend substantially vertically to the lines connecting the fixed contact with the movable contact in the switched-off position or with the current-carrying metal parts of the circuit breaker. Due to the fact that the free end of the bimetallic strip is connected to the conparticles may become deposited on the inner walls of the housing. However, since the fixed contact of the circuit breaker according to the invention is completely surrounded by ribs, these fine metal particles will be deposited only on the surfaces which are directly exposed to the gas current. The recesses between the adjacent ribs which are on the lee side of this gas current remain substantially free of deposits, and they therefore prevent a conductive bridge from being built up between the contacts or between the current-carrying metal parts of the circuit breaker. It is already known to provide circuit breakers with so-called quenching grids which consist of parallel ribs which, however, extend merely between the fixed and movable contacts when the latter is in the switched-off position. These known circuit breakers therefore have the disadvantage that deposits of vaporized contact material may form at points outside of such a quenching grid with the result that the dielectric strength of such circuit breakers when used continuously is relatively low. In the circuit breaker according to the invention, however, it is almost impossible that vaporized contact material may be precipitated on the surfaces of the housing so as to form a conductive bridge since the fixed contact is completely surrounded by ribs which prevent such a bridge formation. In order to increase this eifect, the invention further provides several ribs parallel to each other so that a succession of zones is formed in which no precipitation occurs. This increases the dielectric and short-circuit strength of the circuit breaker according to the invention considerably.

In order to prevent the formation of a bridge of conductive deposits also around the area of the holding detent of the bimetallic strip, the invention further provides a plurality of parallel ribs also around the area of the holding detent at both opposite sides of the housing.

If very high amperages are to be switched oif, the invention further provides the housing of the circuit breaker with slot-shaped apertures in both sides thereof so as to permit an arc and the gases which are thereby produced to emerge from the housing so that the arc will be more quickly extinguished.

For increasing the creeping strength, the housing of the circuit breaker according to the invention is made of creep-resistant insulating material. Materials which are suitable for this purpose are molded and extruded mate-.

rials which contain, for example, melamin resins. Melamin resins also possess a high thermal stability. In order to increase the creep distances, additional insulating parts, for example, bushings, are inserted into the metal parts which might be touched. Thus, for example, the control rod is surrounded and guided by an insulating bushing which is mounted in the bore of the housing by means of a flange which also serves for supporting one end of the return spring of the pushbutton which is loosely coiled around the control rod. The pushbutton is made of a larger diameter than the control rod to which it is secured, thus forming an intermediate shoulder upon which the return spring acts. For insuring a proper operation of this return spring, the same is wound so as to have a trapezoidal shape, and the end of the spring with the larger diameter is mounted on the insulating bushing.

Since the circuit breaker according to the invention has only a single disconnecting point, it is possible to make the fixed contact and the movable contact on the contact bridge of expensive contact material. According to another feature of the invention, these contacts may thus be made of a tungsten-silver alloy which may consist, for example, of 30% of W, 30% of WC and 40% of Ag. For properly securing these small contact plates to the terminal strip and to the vertical strip on the contact bridge, they are provided on their rear side with a herringbone design or any other suitable checked design which is impressed during the soldering operation into the terminal strip and the strip on the contact bridge which may, for example, consist of brass. The soldering operation may be carried out, for example, in a welding machine in Which the respective strip and the contact plate thereon are heated so that the solder which is previously applied upon the herringbone design is melted, While the herring.- bone design on the contact plate is impressed into the strip by the pressure exerted by the welding machine. This manner of securing the contact plates to the terminal strip and to the vertical strip on the contact bridge insures that the contact plates will remain properly and permanently secured to the strips even under very high amperages and at the occurrence of arcs. The terminal strips may be provided in the usual manner either with screw, plug, or soldered connections.

For simplifying the assembly of the circuit breaker according to the invention, the'housing thereof is made of two substantially equal shell-shaped parts which are provided with suitable recesses into which the individual parts of the circuit breaker are inserted and in which they are firmly secured in a fixed position when the two housing parts are secured to each other. a The above-mentioned and other features and advantages of the present invention will become more clearly apparent from the following detailed description thereof, particularly when it is read with reference to the accompanying drawings, in which FIGURE 1 shows a front elevation of an overload circuit breaker according to the invention in the open posi-- tion without the cover part of the housing;

FIGURE 2 shows an elevation of the lower part of the housing of the circuit breaker according to FIGURE 1 Without the switch elements;

FIGURE 3 shows a rear elevation of the cover part for closing the circuit breaker according to FIGURE 1;

FIGURE 4 shows a perspective view of a modification of the overload circuit breaker according to the invention;

FIGURE 5 shows a front elevation of the circuit breaker according to FIGURE 4 but on a larger scale and without the cover part;

FIGURE 6 shows a front elevation of the lower part of the housing of the circuit breaker according to FIG- URE 5;

FIGURE 7 shows a cross section taken along line VII-VII of FIGURE 6;

FIGURE 8 shows a cross section taken along line VIIIVIII of FIGURE 6;

FIGURE 9 shows a perspective rear view of the cover part of the housing according to FIGURE 4 but on a larger scale;

FIGURE 10 shows, partly in cross section, a detail view of a part of FIGURE 5 FIGURE 11 shows a perspective view of a further modification of the overload circuit breaker according to the invention;

FIGURE 12 shows a front elevation of the lower part of the housing of the circuit breaker according to FIG- URE 11 but on a larger scale; while FIGURE 13 shows a rear elevation of the cover part of the housing of the circuit breaker according to FIG- URE 11 but on a larger scale.

Referring first to FIGURES 1 to 3 of the drawings, the circuit breaker according to the invention comprises a housing which consists of substantially equal lower and upper parts 1 and 2 which are secured to each other by rivets, preferably hollow rivets, which are inserted into bores 3 and 3'. For electrically connecting the circuit breaker, two terminal strips 4 and 5 are provided which project from the housing and have connecting screws 6 on their outer ends. Terminal strip 4 is inserted into a corresponding recess 47 in the lower housing part 1 and it is held in a fixed position by the upper housing part 2. On its inner end, terminal strip 4 has a contact 7 which is operatively associated with a movable contact 8 which is secured to the vertical arm of an angular contact bridge 9. The upper arm 9' of contact bridge 9 has a bore through which a control rod 10 extends with a considerable lateral clearance so that contact bridge 9 can move along control rod 10 in the axial direction thereof and can also pivot thereon. The pivot points for this movement of contact bridge 9 are formed by the upper ends of a pair of upright projections 11 (only one of which is shown in FIG. 1) of a control bridge 12 which is rigidly secured to the lower end of control rod 10. The upper arm 9, which according to FIGURE 1 extends almost horizontally, is acted upon by a compression spring 13, the lower end of which rests on control bridge 12. The projections 11 on control bridge 12 also serve for guiding the latter within guide grooves 15 and 15 in the two parts of the housing when the pushbutton 14 which is rigidly secured to the upper end of control rod 10 is being depressed. Control rod10 is additionally guided in the vertical direction by a washer 16 which rests on the bottom of a bore 17 in housing 1, 2. In order to facilitate the insertion of control rod 10,- housing part 1 has a recess 18 for receiving the control rod. Formounting the housing, both parts thereof areprovided with lateral flanges 19 and 20. A compression spring 21 on control rod 10 which acts'at one end upon washer 16 and at the other end upon pushbutton 14 maintains the latter in the position as illustrated in FIGURE 1. This spring 21 is made of a greater strength than the lower spring' 13.

The heating coil 22 for the bimetallic strip 23 is secured at one end to the inner end of terminal strip 23, while its other end is electrically connected to the free end of the bimetallic strip 23. This strip 23 has a punched-out lateral tab 24, the end of which engages with the conical tip of 25 of a setscrew by means of which the holding detent 26 on the bimetallic strip 23 may be accurately adjusted. This holding detent 26 is adapted to arrest contact bridge 9 in its on position. When bimetallio strip 23 bends in the clockwise direction, holding member 26 releases contact bridge 9 so that the latter will be moved by spring 21 into the position as illustrated in FIGURE 1. Compression spring 13 serves for the trip-free release. Thus, if pushbutton 14 is held inthe depressed position, for example, at the occurrence of an excess current when the bimetallic strip is bent in the manner as shown in FIGURE 1, spring 13 will effect a separation of contacts 7 and 8.

The circuit breaker according to FIGURE 1 may also be manually released. For this purpose, a lever 28 is provided which is pivotably mounted on a rivet 27 and has an arm 29 which is adapted to engage with the free end of bimetallic strip 23. If lever 28 is pivoted in a counterclockwise direction, the bimetallic strip will be bent 'in the clockwise direction so that holding detent 26 will release contact bridge 9 in the same manner as if the bimetallic strip is bent because of an excess current.

The vertical arm of contact bridge 9 carries a stranded flexible wire 26' which is secured thereto at the side opposite to and near contact 8, and the other end of which is connected to bimetallic strip 23 on or adjacent to its holding detent 26. Thus, in this embodiment of the overload circuit breaker, no current flows through the bimetallic strip 23 but only through the heating coil 22.

FIGURE 3 illustrates that the cover part 2 of the housing has a projection 18 which engages-into recess 18 of the lower housing part 1 when the two parts are fitted together so that control rod 10 will then be securely held and guided in recess 18.

When the circuit breaker is in the released or off posi tion, as shown in FIGURE 1, arm 9' of contact bridge 9 engages under the action of spring 13 upon an inclined surface 39 in the housing (FIGURE 2), so that control bridge 12 will be swung upon projections 11, whereby a detent 9" on the vertical arm of contact bridge 9 will be placed underneath control bridge 12. When pushbutton 14 is then depressed, control bridge 12 is also moved downwardly and, by engaging with detent 9", it takes along the contact bridge 9 until the right end of arm 9? of the contact bridge engages with and snaps under the holding detent 26 on the bimetallic strip 26 so that, when the pushbutton is then released, contact bridge 9 will be pivoted'in'a'clockwise direction, whereby contact 8 will be connected to the fixed contact 7.

As illustrated in FIGURES 1 to 3, both parts 1 and 2 of the housing are provided with a quenching grid system which consists of ribs 30, 30, 32, 32, 34, 34, 36, and 36. Between these ribs or adjacent thereto are recesses 31, 31', 33, 33', 35, 35, 37, and 37'. If an arc occurs, contacts 7 and 8 will be heated on their surfaces to such an extent that small particles of these surfaces will be vaporized and thrown around and become eventually deposited on the inner sides of the two parts 1 and 2 of the housing. Since the recesses lie within an area adjacent to the ribs and thus within the region sheltered from the gas current, the vaporized and partly oxidized metal particles of the contacts are not deposited at all or only to an inconsiderable extent on the vertical walls of the recesses. Furthermore, due to these ribs, any are which might occur will be split up and will thus be quickly extinguished.

Contacts 7 and 8 are preferably made of a material containing, for example, 30% W, 30% WC and 40% Ag.

As indicated in FIGURE 1, the fixed contact 7 on the three surrounding walls of the housing is completely surrounded by ribs St) to 34. Ribs 36 and 36' have the purpose of quenching an are which might possibly occur between the holding detent 26 and the right end of arm 9' of contact bridge 9. The entire system of quenching ribs is primarily provided for the purpose of avoiding the formation of interconnected conductive deposits on the inner walls of the housing. It causes an interruption of these deposits at those points which face toward the lee side of the gas current which is produced by an arc. Ribs 34 and 34' are offset relatively to each other and of such a height that those on one housing part engage into the recesses between the ribs on the other part. Ribs 30 and 30' also project above ribs 32 and 32'.

According to the embodiment of the invention as illustrated in FIGURES 4 to 10, both parts 1' and 2 of the housing are provided not only with ribs 30, 30', 32, 32', 34, 34', 36, and 36' and the intermediate groovelike recesses, but also with apertures 38 and 38 through which an arc and the gases resulting from it may emerge from the housing. The switch mechanism is the same as in the embodiment according to FIGURES 1 to 3, except that in this case the bimetallic strip 23' is heated directly and is also not provided with a heating coil. For this reason, the bimetallic strip 23' is directly connected to terminal strip This as well as the other terminal strip 4' on which the fixed contact 7 is secured are made in the form of plug contacts.

Pushbutton 14' is guided within a bushing 40 which has screw threads 41 and an annular groove 42 into which the semiannular flanges 43 and 43' project. Pushbutton 14' and control rod are preferably made of one piece of insulating material. Control rod 10' carries a compression spring 21' which acts at one end upon the annular shoulder which is formed by the inner end of the pushbutton and at the other end upon a flange 44 on an insulating bushing 45. Since this insulating bushing 45 has a diameter larger than control rod 10 at its point of connection with pushbutton 14, spring 21' is made of a trapezoidal shape, as shown in FIGURE 10.

The circuit breaker according to FIGURES 11 to 13 is of a construction similar to that of the circuit breakers according to FIGURES 4 to 10, except that the quenching grid system is of a slightly different design. Thus, each housing part 1" and 2" is provided, for example, with three ribs 30 or 30' which are separated by two grooves 31 or 31', respectively. Housing part 1" is fur- 6 ther provided with three ribs 34 which are separated by two grooves 33, while housing part 2 is provided with two ribs 34' and three grooves 33'. Ribs 34 and 34 merge into lower ribs 46 or 46, respectively. From FIGURES 12 and 13 it will be seen that the lowest grooves 33 and 33 merge into the outer grooves 31 or 31, respectively.

As already mentioned, the circuit breaker according to the invention has among others the advantage that it may be made of a very small size at a very high capacity. Thus, the housings of the circuitbreakers are illustrated in FIGURES 4 to 13 may have, for example, a height 46 mm., a width of 29 mm., and a depth of 14 mm.

Although my invention has been illustrated and described with reference to the preferred embodiments thereof, I vw'sh to have it understood that it is in no Way limited to the details of such embodiments, but is capable of numerous modifications within the scope of the appended claims.

Having thus fully disclosed my invention, what I claim is:

1. In an overload circuit breaker, in combination, a housing having parallel opposite inner walls, a fixed contact in said housing located between said inner walls, said housing further containing a contact bridge forming an angular lever having two arms, a contact on one of said arms, and a detent on said one arm, a control bridge having projections thereon engaging with the other arm of said contact bridge, said contact bridge being freely swingable upon said projections for moving the last-mentioned contact into engagement with said fixed contact, a pushbutton within and partly projecting outwardly of said housing, a return spring acting upon said pushbutton and tending to maintain said pushbutton in an outward released position, a control rod rigidly connecting said control bridge to said pushbutton, a spring supported on said control bridge and acting upon said contact bridge, said contact bridge being axially slidable along said control rod against the action of said last-mentioned spring, said housing having an inclined stop surface therein, said contact bridge being pressed by said projections against said inclined stop surface when said pushbutton is in its released position, said control bridge engaging said detent when said pushbutton is depressed whereby said contact bridge is moved away from said inclined surface, thermal releasing means comprising a bimetallic strip mounted at one end on said housing and having a free end, a flexible conductor connecting said free end to said contact bridge, a holding detent on said bimetallic strip near said free end for engaging With and arresting said contact bridge when said pushbutton is fully depressed whereby said contact bridge swings away from said control bridge and said contacts are connected with each other, and a plurality of ribs in each of the opposite inner walls of said housing, and recesses extending between said ribs, said ribs surrounding said fixed contact and being arranged substantially perpendicular to the electric flux lines between said fixed contact and said movable contact when said movable contact is disconnected from said fixed contact, and to the other conductors in said circuit breaker.

2. In a circuit breaker as defined in claim 1, in which said ribs comprise a series of parallel ribs and another series of parallel ribs located lower than the first-mentioned series to provide space for the movement of said contact bridge.

3. In a circuit breaker as defined in claim 1, in which said housing has additional substantially parallel ribs at opposite inner sides thereof within an area adjacent to said holding detent on said bimetallic strip.

4. In a circuit breaker as defined in claim 1, in which said housing has outer walls parallel with said inner walls, and has a plurality of slot-shaped apertures extending therethrough from said inner to said outer walls, and within an area adjacent to said contacts.

5. In a circuit breaker as defined in claim 1, in which said housing consists of a molded material containing melamin resins.

6. In a circuit breaker as defined in claim 1, in which said contacts consist substantially of 30% of W, 30% of WC, and 40% of Ag.

References Cited in the file of this patent UNITED STATES PATENTS Kozacka Dec. 8, 1953 8 Page Jan. 10, 1956 Yeamans July 31, 1956 Ellenberger July 14, 1959 Ellenberger Septf13, 1960 Petermichl et al. Jan. 13, 1961 Gryctko et a1. July 10, 1962 FOREIGN PATENTS Germany Sept. 3, 1959 

1. IN AN OVERLOAD CIRCUIT BREAKER, IN COMBINATION, A HOUSING HAVING PARALLEL OPPOSITE INNER WALLS, A FIXED CONTACT IN SAID HOUSING LOCATED BETWEEN SAID INNER WALLS, SAID HOUSING FURTHER CONTAINING A CONTACT BRIDGE FORMING AN ANGULAR LEVER HAVING TWO ARMS, A CONTACT ON ONE OF SAID ARMS, AND A DETENT ON SAID ONE ARM, A CONTROL BRIDGE HAVING PROJECTIONS THEREON ENGAGING WITH THE OTHER ARM OF SAID CONTACT BRIDGE, SAID CONTACT BRIDGE BEING FREELY SWINGABLE UPON SAID PROJECTIONS FOR MOVING THE LAST-MENTIONED CONTACT INTO ENGAGEMENT WITH SAID FIXED CONTACT, A PUSHBUTTON WITHIN AND PARTLY PROJECTING OUTWARDLY OF SAID HOUSING, A RETURN SPRING ACTING UPON SAID PUSHBUTTON AND TENDING TO MAINTAIN SAID PUSHBUTTON IN AN OUTWARD RELEASED POSITION, A CONTROL ROD RIGIDLY CONNECTING SAID CONTROL BRIDGE TO SAID PUSHBUTTON, A SPRING SUPPORTED ON SAID CONTROL BRIDGE AND ACTING UPON SAID CONTACT BRIDGE, SAID CONTACT BRIDGE BEING AXIALLY SLIDABLE ALONG SAID CONTROL ROD AGAINST THE ACTION OF SAID LAST-MENTIONED SPRING, SAID HOUSING HAVING AN INCLINED STOP SURFACE THEREIN, SAID CONTACT BRIDGE BEING PRESSED BY SAID PROJECTIONS AGAINST SAID INCLINED STOP SURFACE WHEN SAID PUSHBUTTON IS IN ITS RELEASED POSITION, SAID CONTROL BRIDGE ENGAGING SAID DETENT WHEN SAID PUSHBUTTON IS DEPRESSED WHEREBY SAID CONTACT BRIDGE IS MOVED AWAY FROM SAID INCLINED SURFACE, THERMAL RELEASING MEANS COMPRISING A BIMETALLIC STRIP MOUNTED AT ONE END ON SAID HOUSING AND HAVING A FREE END, A FLEXIBLE CONDUCTOR CONNECTING SAID FREE END TO SAID CONTACT BRIDGE, A HOLDING DETENT ON SAID BIMETALLIC STRIP NEAR SAID FREE END FOR ENGAGING WITH AND ARRESTING SAID CONTACT BRIDGE WHEN SAID PUSHBUTTON IS FULLY DEPRESSED WHEREBY SAID CONTACT BRIDGE SWINGS AWAY FROM SAID CONTROL BRIDGE AND SAID CONTACTS ARE CONNECTED WITH EACH OTHER, AND A PLURALITY OF RIBS IN EACH OF THE OPPOSITE INNER WALLS OF SAID HOUSING, AND RECESSES EXTENDING BETWEEN SAID RIBS, SAID RIBS SURROUNDING SAID FIXED CONTACT AND BEING ARRANGED SUBSTANTIALLY PERPENDICULAR TO THE ELECTRIC FLUX LINES BETWEEN SAID FIXED CONTACT AND SAID MOVABLE CONTACT WHEN SAID MOVABLE CONTACT IS DISCONNECTED FROM SAID FIXED CONTACT, AND TO THE OTHER CONDUCTORS IN SAID CIRCUIT BREAKER. 